Near Trondheim there is Trolla in the woods - only a few boulders but quite nice if you have some mossy repellent. You also have Korsvika, right on the shores of the fjord - pleasant enough up to about V5.
Best place I found was Harbak, about 100km north of Trondheim. A field full of perfect granite boulders with stunning views/solitude and only 5 minutes flat walk from the road. There doesn't seem to be a guide for this place, only directions, but you wouldn't need one
There is a Trondheim climbing guide, which you can buy locally. It is in English too, which is a bonus.